THIS invention relates to a locking device, and more specifically to an electromagnetic locking device for a door.
Conventional electromagnetic locks for doors generally include an electromagnet which is arranged to lock an armature plate on a door to a backing plate on a door frame when current is supplied to the electromagnet, and to release the armature plate when the current is interrupted.
The “breaking strength” of these locks, i.e. the force required to overcome the magnetic attraction between the door and the frame so as to cause the door to open, is proportional to the size of the electromagnet. Accordingly, for high security applications it is often necessary to have a large lock or multiple locks which tend to be bulky an often unattractive and which are relatively high in energy consumption.
It is an object of the present invention to provide an electromagnetic lock for a door which has a relatively high breaking strength in relation to the size of the lock and the magnitude of the current drawn by the electromagnet.